1. Field of the Invention
The present invention relates to a hard disk drive. More particularly, the present invention relates to an actuator of a hard disk drive and to a latch system which locks the actuator in position, when the disk of the hard disk drive is stopped, to prevent the actuator from being rotated by an external force.
2. Description of the Related Art
A hard disk drive (HDD) is an information storage device which includes a disk having at least one recording surface, and a read/write head which writes data onto and reads data from the recording surface of the disk while the disk is being rotated. In this respect, the HDD also includes an actuator which moves the read/write head over the recording surface of the rotating disk so that the read/write head can access a desired portion (track) of the recording surface, e.g. a portion onto which data is to be recorded or from which data is to be retrieved.
When the HDD is not in use, that is, when the disk is not rotating, the read/write head is parked at a position away from the recording surface of the disk to prevent the read/write head from colliding against the recording surface of the disk. The parking systems for parking the read/write head include a contact start stop (CSS) type of parking system and a ramp loading type of parking system. In the CSS type of parking system, an inner circumferential part of the disk has a parking zone where no data is recorded, and the read/write head is parked in contact with the parking zone. In the ramp loading type of parking system, a ramp is disposed radially outwardly of the disk, and the actuator is moved onto the ramp to park the read/write head.
However, in either case, an external force applied to the HDD, e.g., an impact or vibrations, could move the actuator arbitrarily while the read/write head is parked. Thus, such an external force could move the read/write head onto the recording surface of the disk. As a result, the read/write head or the recording surface of the disk could be damaged. In view of such a potential problem, the actuator is “locked” when the read/write head is parked so that the read/write head will remain in the parking zone or adjacent the ramp even when an external force is applied to the HDD. A variety of known actuator latch systems are employed by HDDs for this purpose.
FIGS. 1A, 1B, and 1C illustrate an example of a conventional actuator latch system 20, known as a single lever type of inertial latch system, of an HDD. In this example, the HDD employs a ramp loading type of parking system having a ramp 15.
Referring to FIG. 1A, an actuator 10 for moving a read/write head (not shown) to a desired position over a disk (also not shown) includes a swing arm 12 supported by a pivot 11 so as to be rotatable about an axis, and a suspension 13 disposed at an end portion of the swing arm 12. The suspension 13 supports a slider 14 to which the read/write head is mounted, and elastically biases the read/write head toward the recording surface of the disk. The inertial latch system 20 includes a latch lever 21 supported so as to be freely rotatable about an axis parallel to that about which the swing arm 12 is rotated, a crash stop 24 limiting the clockwise rotation of the swing arm 12, and a latch stop 25 limiting the clockwise rotation of the latch lever 21. The latch lever 21 has a latch hook 22 at a leading end portion thereof. The swing arm 12, on the other hand, defines a notch 23 in an end thereof that faces the latch lever 21.
FIG. 1B shows the case in which a shock applied to the HDD causes the swing arm 12 of the actuator 10 and the latch lever 21 to rotate counterclockwise due to their moments of inertia. Accordingly, the latch hook 22 is received in the notch 23 such that the swing arm 12 of the actuator 10 cannot rotate any further in the counterclockwise direction. In contrast, FIG. 1C shows the case in which a shock applied to the HDD causes the swing arm 12 of the actuator 10 and the latch lever 21 to rotate clockwise due to their moments of inertia. In this case, the swing arm 12 collides against the crash stop 24, rebounds, and thereby begins to rotate counterclockwise. The latch lever 21 collides against the latch stop 25, rebounds and thereby also rotates counterclockwise. Accordingly, the latch hook 22 is received in the notch 23 so that the actuator 10 is basically locked in place.
The conventional single lever type of inertia latch system 20 operates relatively reliably when the shock applied to the HDD causes the swing arm 12 of the actuator 10 to initially rotate counterclockwise. However, in the case in which shock applied to the HDD causes the actuator 10 and the latch lever to rotate clockwise and then rebound from the crash stop 24 and latch stop 25, respectively, the resulting counterclockwise rotation of the swing arm 12 may not be timed with that of the latch lever 21. That is, sometimes the latch hook 22 does not engage the swing arm 12.
Also, as described above, counterclockwise rotation of the swing arm 12 is normally limited by the engagement between the latch lever 21 and the swing arm 12 when the latch hook 22 is received in the notch. However, when the external shock which causes the swing arm 12 to rotate counterclockwise is relatively great, the latch hook 22 and the swing arm 12 collide with each other with such force that the swing arm 12 and the latch lever 21 rebound from each other. Accordingly, the swing arm 12 rotates clockwise, collides against the crash stop 24, rebounds and then starts rotating counterclockwise. In this case, the counterclockwise rotation of the swing arm 12 is often not limited by the latch hook 22, due to a mismatch in the timing of the latch system as described above.
Therefore, the swing arm 12 continues to rotate counterclockwise, and the read/write head moves off of the ramp 15 and onto the recording surface of the disk. Accordingly, the read/write head or the recording surface of the disk may be damaged.
FIGS. 2A, 2B, and 2C illustrate a dual lever type of inertia latch system 40 that was developed to overcome the above-described problems of the conventional single lever type of inertia latch system 20. Reference numeral 30 designates the actuator of the HDD, and reference numeral 32 designates the swing arm 32 of the actuator 30.
Referring to FIG. 2A, the inertia latch system 40 includes two latch levers 41 and 42 each supported so as to be freely rotatable about a respective axis, and a crash stop 46 limiting the clockwise rotation of the swing arm 32. Also, the first latch lever 41 has a latch pin 43, whereas the second latch lever 42 has a latch hook 44. The swing arm 32 of the actuator 30 defines a notch 45 at an end thereof which faces the second latch lever 42.
FIG. 2B shows the case in which shock applied to the HDD causes the swing arm 32 of the actuator 30 and the first and second latch levers 41 and 42 to rotate counterclockwise due to their moments of inertia. Accordingly, the swing arm 32 of the actuator 30 is caught by the second latch lever 42, i.e., the latch hook 44 is received in the notch 45, whereupon the swing arm 32 cannot rotate any further in the counterclockwise direction. In contrast, FIG. 2C shows the case in which shock applied to the HDD causes the swing arm 32 of the actuator 30 and the first latch lever 41 to rotate clockwise due to their moments of inertia. The swing arm 32 then collides with the crash stop 46, rebounds and thereby starts rotating counterclockwise. At the same time, the clockwise rotation of the first latch lever 41 causes the latch pin 43 to engage the second latch lever 42 and thereby cause the second latch lever 42 to rotate counterclockwise. As a result, the latch hook 44 is received in the notch 45 such that the second latch lever 42 engages the swing arm 32. Accordingly, the swing arm 32 is prevented from rotating further in the counterclockwise direction.
The conventional dual lever type of inertia latch system 40 operates reliably with respect to shock applied to the HDD which creates a moment acting on the swing arm 32 in either a clockwise or counterclockwise direction. However, the dual lever type of inertia latch system 40 is complex and requires a relatively large amount of space. Accordingly, the dual lever type of inertia latch system 40 is costly to fabricate and assemble, and is difficult to provide in a compact mobile disk drive.